Aqueous Reactions Dr. Ron Rusay. Aqueous Reactions There are several general types: 1) Precipitation: An insoluble salt forms from the addition of solutions.

Aqueous Reactions

Dr. Ron Rusay

Aqueous Reactions There are several general types:

1) Precipitation: An insoluble salt forms from the addition of solutions. (Refer to Solubility Rules)

2) Acid-Base Reactions (Neutralization) generally produces a salt plus water

3) Oxidation-Reduction (Redox) there is a change in oxidation numbers between reactants and products

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Solution Test Apparatusfor Electrolytes

Conductivity

Electrolytes Aqueous solutions can be categorized into 3

types: non-electrolytes, strong electrolytes or weak electrolytes based on their ability to conduct electricity.

A solution must have ions to conduct. Pure Water does not conduct. Aqueous solutions can be tested for conductivity

which will determine the degree of ionization of the solutes.

It is possible to have full or partial ionization.

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Electrolytes Almost all ionic compounds and a few molecular

compounds are strong electrolytes. Several molecular compounds are weak

conductors, most are non-conductors. Conductivity is directly related to the amount of

ionization, i.e. ions in solution. Table salt, sodium chloride, is completely ionized:

NaCl(s) + H2O(l) NaCl(aq) 0.10M Na

+(aq) + Cl -

(aq) 0.00M 0.10M 0.10M

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Molarity (M) = Moles solute / Liter solution

Electrolytes

Concentrations: CaCl2 (s) + H2O(l) CaCl2(aq) 0.10M

Ca 2+

(aq) + 2 Cl -(aq) 0.00M

0.10M 0.20M

Molarity (M) = Moles solute / Liter solution

Electrolytes Sugars like sucrose are non-ionic, molecular

compounds that dissolve but produce no ions.

C12H22O11 (S) + H2O(l) C12H22O11 (aq)

Some molecular compounds like acetic acid ionize partially (dissociate) in water

HC2H3O2 (l) + H2O(l) H3O+(aq)+

0.1000M C2H3O2 -(aq)

0.9987M 0.0013M

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Molarity (M) = Moles solute / Liter solution

Aqueous Acids

Any compound that provides a proton can be considered an acid. Strong acids are sulfuric acid, nitric acid, perchloric acid, HI, HBr and HCl.

Electrolytes

How would the conductivity of acetic acid compare to hydrochloric acid?

HCl Completely Ionized

Acetic Acid (HC2H3O2)

Aqueous Bases

Any compound that accepts a proton is a base. The common bases are group IA & IIA metal hydroxide

compounds. They are strong bases, dissociating completely in water.

An example of a weak base is ammonia.

NH3 (g) + H2O(l) NH3 (aq) NH4+

(aq)+ OH-(aq)

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⇔ ⇔

An Aqueous Solution of Sodium Hydroxide

NH3 in Water

QUESTION

Aqueous Reactions: Neutralization

Aqueous Reactions: Neutralization Net Ionic Equations

HCl(aq) + NaOH (aq) NaCl (aq) + H2O(l) ___________________________________________________

HCl(aq) H+(aq) + Cl -

(aq)

NaOH (aq) Na+(aq)+ OH-

(aq)

NaCl (aq) Na+(aq)+ Cl-

(aq) ________________________________________________

Na+(aq)+ OH-

(aq) + H+(aq) + Cl -

(aq)

Na+(aq)+ Cl-

(aq) + H2O(l) _______________________________________________________

H+(aq) + OH -

(aq) H2O(l)

An aqueous solution of H2SO4 is added to aqueous Ba(OH)2. The reaction is monitored using a conductivity tester. Predict the correct statement(s).

I) Both H2SO4 and Ba(OH)2 are strong electrolytes.

II) This is a neutralization reaction.

III) This is a precipitation reaction.

IV) The light bulb will glow at the neutralization point.

A) II B) I and II

C) I, II and III D) I, II, III and IV

QUESTION

Aqueous Reactions: Acid-Base

QUESTIONIf an antacid contains Al(OH)3 it will form AlCl3 upon neutralization of stomach acid. How many moles of Cl– ions are in 100.0 mL of 0.010 M AlCl3?

A.0.0010 MB.0.010 MC.0.0030 MD.0.030 M

Molarity (M) = Moles solute / Liter solution

QUESTION

How do you know the state of the products?

What type of reaction is it?

Write a balanced equation for the reaction.

QUESTIONGiven the insoluble compound Al2(CO3)3 predict the ions and coefficients that would be necessary to complete the following net ionic equation:

__ _____ + ____ _____ Al2(CO3)3

A.2 AlCl3 + 3 Na2CO3 also include 6 NaCl on rightB.3 Al3+ + 2 CO3

2–

C.2 Al3+ + 3 CO32–

D.2 Al3+ 6 Cl – + 3 CO32– + 6 Na+

Aqueous Reactions: PrecipitationNet Ionic Equations

50mL of a 0.1M solution of sodium sulfate is mixed with 50mL of a 0.2M solution of silver nitrate. What is the result?

Molecular Equation:

?Na2SO4(aq)+ ?AgNO3(aq)

?Ag2SO4(s) + ?NaNO3(aq)

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1 2

1 2

Aqueous Reactions: PrecipitationNet Ionic Equations

Na2SO4(aq)+ 2 AgNO3(aq) Ag2SO4(s)+ 2 NaNO3(aq)

0.1M 0.2M Ionic Reaction (Reactants):

Na2SO4(aq) 2 Na+(aq) + SO4

2-(aq)

2 AgNO3(aq) 2 Ag+(aq) + 2 NO3

1-(aq)

2 Na+(aq)+ SO4

2-(aq)+ 2 Ag+

(aq)+ 2 NO31-

(aq)

0.2M 0.1M 0.2M 0.2M

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Aqueous Reactions: PrecipitationNet Ionic Equations

Na2SO4(aq)+ 2 AgNO3(aq) Ag2SO4(s)+ 2 NaNO3(aq)

0.1M 0.2M Ionic Reaction (Products):

2 NaNO3(aq) 2 Na+(aq) + 2 NO3

1-(aq)

Ag2SO4(s) Does not dissolve (ionize)

2Na+(aq)+ 2NO3

1-(aq) + Ag2SO4(s)

0.2M 0.2M solid

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Aqueous Reactions: PrecipitationNet Ionic Equations

Na2SO4(aq)+ 2 AgNO3(aq) Ag2SO4(s)+ 2 NaNO3(aq)

Overall Ionic Reaction:

2Na+(aq)+ SO4

2-(aq) +2Ag+

(aq)+ 2NO31-

(aq)

2Na+(aq) + Ag2SO4(s) + 2NO3

1-(aq)

Net Ionic Equation: (Subtract Spectator Ions)

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2Ag+(aq)+ SO4

2-(aq) Ag2SO4(s)

= MNa2SO4 xVNa2SO4 / 1:1stoichiometry

= 0.10M x 0.050 L/ 1= 0.0050 mol

How many moles?

M x Vsolution= mol

QUESTION

Pb(NO3)2 (aq) + NaI (aq) NaNO3(aq) + PbI 2(s)

Write a balanced Net Ionic equation for the reaction.

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What are the spectator ions in the reaction?

QUESTION

QUESTIONIf you began a reaction with the following ions in solution (all would be written with an (aq) subscript how would you represent the proper final net ionic equation? (Consult a solubility Table.)

6Na+ + 2PO43– + 3Fe2+ + 6NO3

–

A. 3Na+ + PO43– + Fe2+ + 2NO3

– No ReactionB. 6Na+ + 2PO4

3– + 3Fe2+ + 6NO3– Fe3(PO4)2 (s)+ 6NaNO3

C. 3Na+ + PO43– + Fe2+ + 2NO3

– Fe3(PO4)2 (s)+ 6 Na+ + 6 NO3–

D. 2PO43– + 3Fe2+ Fe3(PO4)2 (s)

Oxidation-Reduction

Oxidation is the loss of electrons. Reduction is the gain of electrons. The reactions occur together. One does

not occur without the other. The terms are used relative to the

change in the oxidation state or oxidation number of the reactant(s).

Aqueous Reactions:Oxidation - Reduction

In the following reaction, identify what is being oxidized and what is being reduced. What is the total number of electrons involved in the process?

Oxidation Reduction Reactions

QUESTIONIn a redox reaction, oxidation and reduction must both occur. Which statement provides an accurate premise of redox chemistry?

A.The substance that is oxidized must be the oxidizing agent.B.The substance that is oxidized must gain electrons.C.The substance that is oxidized must have a higher oxidation

number afterwards.D.The substance that is oxidized must combine with oxygen.

QUESTION